U.S. patent application number 13/240737 was filed with the patent office on 2012-05-24 for golf club grip.
This patent application is currently assigned to BRIDGESTONE SPORTS CO., LTD. Invention is credited to Hiromasa ITO, Yoshifumi NAKAJIMA, Tadahiro TAKECHI.
Application Number | 20120129624 13/240737 |
Document ID | / |
Family ID | 46064862 |
Filed Date | 2012-05-24 |
United States Patent
Application |
20120129624 |
Kind Code |
A1 |
ITO; Hiromasa ; et
al. |
May 24, 2012 |
GOLF CLUB GRIP
Abstract
A golf club grip having a double construction includes a
cylindrical inside layer part made of a first rubber having a first
hardness, and a cylindrical outside layer part made of a second
rubber having a second hardness lower than the first hardness,
which part covers the cylindrical inside layer part. The
cylindrical inside layer part has a length 1 to 4 cm longer than
the length of a half of the entire length of the grip. The
cylindrical inside layer part is provided with a plurality of
longitudinal projecting strips formed on the outer peripheral
surface thereof, and the plurality of longitudinal projecting
strips extend from the proximal end side of the cylindrical inside
layer part to a portion of 70 to 80% of the entire length of the
cylindrical inside layer part along the axis line direction of the
cylindrical inside layer part, and are formed at fixed intervals in
the circumferential direction. The cylindrical outside layer part
is provided with a plurality of circumferential grooves, which are
formed at fixed intervals in the axis line direction, on the outer
peripheral surface of a portion covering a portion of the
cylindrical inside layer part in which the longitudinal projecting
strips are formed. The cylindrical outside layer part is provided
with a plurality of longitudinal grooves formed on the outer
peripheral surface on the distal end side of the circumferential
grooves.
Inventors: |
ITO; Hiromasa; (Tokyo,
JP) ; NAKAJIMA; Yoshifumi; (Tokyo, JP) ;
TAKECHI; Tadahiro; (Tokyo, JP) |
Assignee: |
BRIDGESTONE SPORTS CO., LTD
Tokyo
JP
|
Family ID: |
46064862 |
Appl. No.: |
13/240737 |
Filed: |
September 22, 2011 |
Current U.S.
Class: |
473/303 ;
473/300 |
Current CPC
Class: |
A63B 60/00 20151001;
A63B 2209/00 20130101; C08L 23/16 20130101; C08K 3/30 20130101;
C08L 7/00 20130101; A63B 60/48 20151001; C08L 7/00 20130101; A63B
53/14 20130101; C08L 23/16 20130101; C08K 3/08 20130101; C08K
2003/3045 20130101 |
Class at
Publication: |
473/303 ;
473/300 |
International
Class: |
A63B 53/14 20060101
A63B053/14 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 22, 2010 |
JP |
2010-259676 |
Dec 13, 2010 |
JP |
2010-276828 |
Apr 22, 2011 |
JP |
2011-095899 |
Apr 22, 2011 |
JP |
2011-095900 |
Claims
1. A golf club grip having a double construction, comprising: a
cylindrical inside layer part made of a first rubber having a first
hardness, the cylindrical inside layer part having a length 1 to 4
cm longer than the length of a half of the entire length of the
grip; and a cylindrical outside layer part made of a second rubber
having a second hardness lower than the first hardness, which
covers the cylindrical inside layer part, wherein the cylindrical
inside layer part comprises a plurality of longitudinal projecting
formed on the outer peripheral surface thereof, the plurality of
longitudinal projecting strips extending from the proximal end side
of the cylindrical inside layer part to a portion of 70 to 80% of
the entire length of the cylindrical inside layer part along the
axis line direction of the cylindrical inside layer part, and being
formed at fixed intervals in the circumferential direction; the
cylindrical outside layer part comprises plural circumferential
grooves, which are formed at fixed intervals in the axis line
direction, on the outer peripheral surface of a portion covering a
portion of the cylindrical inside layer part in which the
longitudinal projecting strips are formed; and the cylindrical
outside layer part comprises a plurality of longitudinal grooves
formed on the outer peripheral surface on the distal end side of
the circumferential grooves.
2. The golf club grip according to claim 1, wherein as for the wall
thicknesses of the cylindrical inside layer part and a portion of
the cylindrical outside layer part which covers the cylindrical
inside layer part, the cylindrical inside layer part is formed so
as to be thicker than the cylindrical outside layer part.
3. The golf club grip according to claim 1, wherein the cylindrical
inside layer part is provided with a ring-shaped protrusion
extending in the circumferential direction on the distal end side
of the area in which the longitudinal projecting strips are formed;
and the cylindrical outside layer part covers the portion of the
cylindrical inside layer part in which the longitudinal projecting
strips are formed, and is provided with a first cylindrical outside
layer part ranging from the proximal end side of the cylindrical
inside layer part to the ring-shaped protrusion and a second
cylindrical outside layer part ranging from the ring-shaped
protrusion to the grip distal end, which covers the distal end side
of the ring-shaped protrusion of the cylindrical inside layer part,
and the first cylindrical outside layer part and the second
cylindrical outside layer part have different colors.
4. The golf club grip according to claim 3, wherein as for the wall
thicknesses of the cylindrical inside layer part and a portion of
the cylindrical outside layer part which covers the cylindrical
inside layer part, the cylindrical inside layer part is formed so
as to be thicker than the cylindrical outside layer part.
5. The golf club grip according to claim 3, wherein the second
cylindrical outside layer part constituting the cylindrical outside
layer part has a hardness higher than that of the first cylindrical
outside layer part.
6. A golf club grip comprising: a cylindrical and rubber inside
layer part; a cylindrical and rubber outside layer part which
covers the inside layer part; and a tungsten sheet having a
thickness of 0.2 to 2.0 mm, which is located between the inside
layer part and the outside layer part.
7. The golf club grip according to claim 6, wherein the tungsten
sheet is formed by molding a mixture of a thermoplastic resin
material and tungsten powder, and has a specific gravity of 8 or
more.
8. The golf club grip according to claim 6, wherein the inside
layer part is formed so as to be 1 to 4 cm longer than the length
of a half of the entire length of the grip, and the inside layer
part is thicker than the outside layer part.
9. The golf club grip according to claim 6, wherein the tungsten
sheet has a width of 5 to 10 mm and a length of 80 to 120 mm.
10. A golf club grip having a double construction, comprising: a
cylindrical inside layer part made of a first rubber compound
having a first specific gravity; and a cylindrical outside layer
part made of a second rubber compound having a second specific
gravity smaller than the first specific gravity, which part covers
the inside layer part, wherein the inside layer part is shorter
than the outside layer part.
11. The golf club grip according to claim 10, wherein the inside
layer part contains at least one of barium sulfate and metal
powder, and the specific gravity thereof is 1.3 to 1.6.
12. The golf club grip according to claim 10, wherein the specific
gravity of the outside layer part is 1.0 to 1.15.
13. The golf club grip according to claim 10, wherein the inside
layer part has a plurality of longitudinal projecting strips on the
outer peripheral surface.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This Application claims priorities from Japanese Patent
Application No. 2010-259676 filed Nov. 22, 2010, Japanese Patent
Application No. 2010-276828 filed Dec. 13, 2010, Japanese Patent
Application No. 2011-95899 filed Apr. 22, 2011, and Japanese Patent
Application No. 2011-95900 filed Apr. 22, 2011, which are
incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a golf club grip.
[0003] Generally, a golf club is formed with a head, a shaft, and a
grip. The conventional grip is formed of rubber, the main component
of which is, for example, natural rubber. By forming the grip of
such a material, the grip feel at the time when a golfer grips a
golf club is improved, the anti-slipping effect of the grip is
improved, and the resistance to deterioration in the grip is
improved.
[0004] Japanese Utility Model Application Publication No. 62-9476
discloses a grip that is formed of a material having a two-layer
construction consisting of an inside layer part and an outside
layer part, in which the inside layer part is softer than the
outside layer part throughout the entire length of the grip. Also,
Japanese Utility Model Application Publication No. 62-82066
discloses a grip that is formed of a two-layer material in which
the inside layer part is harder than the outside layer part
throughout the entire length of the grip to improve the grip
feel.
[0005] Generally, when a golfer grips a golf club grip, the
proximal end side of the grip is gripped by one hand as the axis at
the swinging time, and the other hand is attached to the one hand
on the distal end side of the grip to feel the ball hitting feeling
by means of the palm of the other hand. Therefore, if the grip is
made soft, the ball hitting feeling is not transmitted very much,
and on the other hand, if the grip is made hard, the grip is not
broken in to the hand, and moreover strong ball hitting vibrations
are transmitted too greatly to the hand serving as the axis of
swing, so that an adverse influence is exerted on the wrist and the
elbow.
[0006] The grip described in Japanese Utility Model Application
Publication No. 62-9476 has a drawback in that the hand gripping
the distal end side of the grip is less liable to feel the ball
hitting feeling. The grip described in Japanese Utility Model
Application Publication No. 62-82066 has a problem in that the grip
is less liable to be broken in to the hand gripping the proximal
end side of the grip, and moreover heavy ball hitting vibrations
are transmitted to the elbow and the like.
[0007] Also, the way of gripping the golf club (the manner of
gripping) is very important for controlling the height, carry, and
direction of shot. As the manner of gripping, Vardon grip,
interlock grip, and the like can be used. In any manner of
gripping, in the case in which the proximal end side of the grip is
gripped by one hand as the axis of swing, the golf club is held
stably by attaching the thumb of the one hand onto the grip to
determine the direction of the golf club.
[0008] Japanese Utility Model Registration No. 2533541 discloses a
grip in which the ball hitting feeling can be felt satisfactorily
by the hand attached to the distal end side of grip, the gripping
feeling is good and strong ball hitting vibrations are not
transmitted to the wrist, elbow, etc. of the hand gripping the
proximal end side of grip, and moreover a hook or slice of a shot
can be prevented positively by supporting the belly of the thumb of
that hand. This grip is a golf club grip formed of a material
having a two-layer construction consisting of an inside layer part
and an outside layer part, in which the inside layer part on the
proximal end side of the grip is softer than the outside layer part
thereon, and the inside layer part on the distal end side of the
grip is harder than the outside layer part thereon.
[0009] Also, a grip formed of a silicone resin, not formed of
rubber, is described in Japanese Patent Application Publication No.
2010-188019. This grip can restrain the shift of the collision
angle between the head face and the ball. Conventionally, it has
been thought that the shift of ball hitting direction results from
the torsion of the shaft. However, even if the torsional rigidity
of the shaft is improved, there occurs a phenomenon that the ball
hitting direction shifts from the direction intended by the golfer.
In the study on the causes for this phenomenon, the present
inventor paid attention to the fact that the grip, which is a
constituent element of the golf club, is far more elastic than the
shaft. That is, the present inventor obtained knowledge that
although it is apparent that the impact force produces the
torsional deformation of the shaft, the shift of the collision
angle between the head face and the ball depends greatly on the
elastic deformation of grip caused by the impact force. As a
result, the grip described in Japanese Patent Application
Publication No. 2010-188019 has been developed.
[0010] The grip described in Japanese Patent Application
Publication No. 2010-188019 is a golf club grip including a
cylindrical inside layer part formed of a first resin and a
cylindrical outside layer part that is insert molded using a second
resin having a lower hardness than that of the first resin so as to
cover the cylindrical inside layer part with the cylindrical inside
layer part being used as an insert member. In this grip, engagement
protrusions engaging with the cylindrical outside layer part are
provided on the outer peripheral surface of the cylindrical inside
layer part, and the engagement protrusions are arranged in parallel
in the circumferential direction at a first pitch and arranged in
parallel in the longitudinal direction at a second pitch.
[0011] Also, to improve the feeling of ease of swinging of the golf
club, the weight of the grip is also adjusted. The weight of recent
golf clubs has become lighter as a whole due to the development of
new head materials and the reduced weights of shafts. The lighter
golf club increases the head speed, which leads to an increase in
carry of a hit ball, but poses a problem that a mistake shot may
occur because of inconstant trajectory of swing caused by bringing
the golf club onto an erroneous trajectory because of its lightness
when the golf club is swung up or when the swung-up golf club is
swung down.
[0012] To solve this problem, there has conventionally been known a
golf club in which a heavy substance, what is called a
counterbalancing member, is mounted on the golf club grip. The golf
club of this type has been configured as described below. The
counterbalancing member is, for example, a thin sheet made of lead,
and is wound on a portion near the grip end, in which a grip member
is to be mounted on the club shaft, of the club shaft. Thereafter,
the ordinarily used grip member is fitted onto the shaft from over
the thin sheet made of lead wound on the shaft, and is fixed to the
shaft with an adhesive or the like. Alternatively, a separate
member including a weight is mounted at the grip end of the grip
member (refer to Japanese Patent Application Publication No.
6-142244). In this case, the moment of inertia of the golf club
with the grip being a pivot point is unchanged before and after the
counterbalancing member is mounted, so that even a golf player
having little strength can use a relatively heavy golf club.
Therefore, even if the golf player uses the relatively heavy golf
club, the player can give the same carry of golf ball as in the
case of using the lightweight golf club. Furthermore, since the
weight of the entire golf club can be increased, swinging can be
performed in a correct and stable trajectory, and therefore a
mistake shot can be prevented.
[0013] With the method in which the counterbalancing member is
mounted on the grip, uncomfortable feeling is given to the golf
player, and also the appearance is bad. Accordingly, there has been
developed a golf club grip in which an auxiliary member is embedded
in the grip itself (refer to Japanese Patent Application
Publication No. 11-319172). This grip is formed mainly of an
elastic body such as rubber, and is manufactured by molding a
semi-cylindrical base material half body constituting a region on
the outside of the shaft center axis line and a semi-cylindrical
base material half body constituting a region on the inside (back
surface side), and then by bonding these two half bodies so as to
face to each other. By containing a metallic material in the base
material half body constituting a region on the inside to increase
the weight of this base material half body, the weight of the base
material half body constituting a region on the inside is made 5 to
30 g heavier than the weight of the base material half body
constituting a region on the outside. For example, metal powder is
contained in the base material half body constituting a region on
the inside, or metal fibers or metal sheets are contained in the
base material half body constituting a region on the inside. As the
metal, a metal material consisting of tungsten, titanium, aluminum,
nickel, boron, titanium-nickel alloy, lead, copper, silver, gold,
low-carbon steel, and the like can be used, and it is said that
tungsten is especially preferable.
SUMMARY OF THE INVENTION
[0014] The grip described in Japanese Utility Model Registration
No. 2533541 solves problems in Japanese Utility Model Application
Publication No. 62-9476 and Japanese Utility Model Application
Publication No. 62-82066, and is configured so that because, on the
proximal end side of grip gripped by the hand serving as the axis
of swing (the left hand for a right-handed person), the inside
layer part formed of a soft material is deformed, the grip can be
gripped surely, the grip feel is good, and the ball hitting feeling
is satisfactorily transmitted from the inside layer part formed of
a hard material to the hand on the distal end side (the right
hand). However, it has been desired to further improve the grip
feel and the ball hitting directivity.
[0015] The grip described in Japanese Patent Application
Publication No. 2010-188019 is formed of a silicone resin, not
formed of rubber, so that the torsional rigidity is improved as
compared with the rubber grip. However, when this grip is mounted
on the shaft, the solvent for mounting (white gas) takes a long
time to vaporize. To examine this phenomenon, the portion in which
the grip is in contact with the shaft was observed by cutting the
grip one week after the grip had been mounted, and as a result, it
was found that the inner peripheral surface of grip was wet (the
solvent did not vaporize sufficiently). That is, the force for
bonding the grip to the shaft was weak.
[0016] Accordingly, an object of the present invention is to
provide a golf club grip in which the gripping feeling and the ball
hitting directivity are improved, and the force for bonding the
grip to the shaft is strong.
[0017] Also, a grip having a multi-colored appearance has been on
the market. However, the boundary of color is unclear, for example,
because colors are mixed in the joint portion of rubber products
having different colors, and no grip in which colors are divided
clearly is found. Even if colors are divided clearly by using
rubbers having different colors, the demands have not been met in
terms of clarifying the roles of the right and left hands and
enhancing the fashionability.
[0018] Accordingly, another object of the present invention is to
provide a golf club grip in which the gripping feeling and the ball
hitting directivity are improved, the force for bonding the grip to
the shaft is strong, and the colors are divided clearly.
[0019] Furthermore, according to the invention disclosed in
Japanese Patent Application Publication No. 11-319172, a difference
in weight is made so that the base material half body located in
the region on the inside of the shaft center axis line is heavier
than the base material half body located in the region on the
opposite side, that is, on the outside of the shaft center axis
line (the head side). This difference in weight is 5 to 30 g,
preferably 10 to 25 g. By this difference in weight, the weight
ratio between the outside and the inside with respect to the shaft
center axis line of the whole of golf club is decreased, so that it
is said that the stability at the swinging time is improved, and
the operability of the club and the reproducibility of swing are
improved. If the difference in weight is less than 5 g, the effects
of the present invention cannot be achieved sufficiently. If the
difference in weight is greater than 30 g, the weight of grip
becomes too heavy, and the total balance of golf club is disturbed
unfavorably.
[0020] In this conventional example, to embed metal fibers (for
example, tungsten) in the rubber base material half body
constituting the region on the inside, the metal fibers should be
set exactly in the mold beforehand when this base material half
body is molded by vulcanization, which requires much time and
labor. Also, since the torsional rigidities of the base material
half bodies on the inside and on the outside are different, the
torsional deformation of the grip at the time when a golfer hits a
ball is different between the inside half and the outside half, so
that there is a fear that the hit ball will not fly in the
direction intended by the golfer.
[0021] Accordingly, still another object of the present invention
is to provide a golf club grip in which counterbalance is achieved,
the ease of swing is increased, a shift of collision angle caused
by the torsional deformation at the time when the head collides
with the ball is prevented, and also the manufacture is easy.
[0022] Also, in the above-described conventional example, the
gripping feeling (swinging feeling, etc.) for each base material
half body is different, so that some golfers have an uncomfortable
feeling.
[0023] Accordingly, still another object of the present invention
is to provide a golf club grip in which counterbalance is achieved,
the ease of swinging is increased, a shift of collision angle
caused by the torsional deformation at the time when the head
collides with the ball is prevented, and the grip feel is good.
[0024] A first mode of the present invention is a golf club grip
having a double construction in which a rubber cylindrical inside
layer part is covered by a rubber cylindrical outside layer part
having a hardness lower than that of the cylindrical inside layer
part, wherein the cylindrical inside layer part is formed so as to
be 1 to 4 cm longer than the length of a half of the entire length
of the grip; the cylindrical inside layer part is formed so as to
be harder than the cylindrical outside layer part; a plurality of
longitudinal projecting strips are formed at fixed intervals in the
circumferential direction on the outer peripheral surface of the
cylindrical inside layer part so as to extend from the proximal end
side of the cylindrical inside layer part to a portion of 70 to 80%
of the entire length of the cylindrical inside layer part along the
axis line direction of the cylindrical inside layer part; a
plurality of circumferential grooves are formed at fixed intervals
in the axis line direction on the outer peripheral surface of a
portion of the cylindrical outside layer part that covers a portion
of the cylindrical inside layer part in which the longitudinal
projecting strips are formed; and a plurality of longitudinal
grooves are formed on the outer peripheral surface on the distal
end side of the circumferential grooves of the cylindrical outside
layer part.
[0025] According to the first mode of the present invention, by the
above-described configuration, the cylindrical outside layer part
and the cylindrical inside layer part can be integrated, the
torsion of the whole of the grip can be prevented by the
combination of the longitudinal projecting strips and the
circumferential grooves, and the presence of the circumferential
grooves can resist the centrifugal force of the head at the
swinging time on the grip proximal end side. Therefore, the
gripping feeling on the grip proximal end side (the portion gripped
by the left hand for a right-handed person) is harder than the
gripping feeling on the grip distal end side (the portion gripped
by the right hand), so that the torsion of the portion gripped by
the left hand, which serves as the axis at the swinging time,
becomes small. Therefore, the ball hitting directivity is improved,
and moreover, since the cylindrical outside layer part is soft, an
adverse influence of ball hitting vibration is less liable to
occur. Also, in the case in which the cylindrical inside layer part
is made of rubber, and the grip is fixed to the shaft by using a
common solvent for mounting (white gas) and a double-faced adhesive
tape, the solvent vaporizes in a short period of time, and the
fixing of the grip to the shaft becomes firm in a short period of
time of about a half day or even less.
[0026] A second mode of the present invention is a golf club grip
having a double construction in which a rubber cylindrical inside
layer part is covered by a rubber cylindrical outside layer part
having a hardness lower than that of the cylindrical inside layer
part, in which the cylindrical inside layer part is formed so as to
be 1 to 4 cm longer than the length of a half of the entire length
of the grip; a plurality of longitudinal projecting strips are
formed at fixed intervals in the circumferential direction on the
outer peripheral surface of the cylindrical inside layer part so as
to extend from the proximal end side of the cylindrical inside
layer part to a portion of 70 to 80% of the entire length of the
cylindrical inside layer part along the axis line direction of the
cylindrical inside layer part; a ring-shaped protrusion is formed
in the circumferential direction on the distal end side of the
portion in which these longitudinal projecting strips are formed; a
plurality of circumferential grooves are formed on the outer
peripheral surface of a first cylindrical outside layer part, which
covers the portion in which these longitudinal projecting strips
are formed and is formed in the portion between the proximal end
side and the ring-shaped protrusion, so as to be at fixed intervals
in the axis line direction; a second cylindrical outside layer
part, which covers the distal end side of the ring-shaped
protrusion of the cylindrical inside layer part and ranges from the
ring-shaped protrusion to the grip distal end, is formed; a
plurality of longitudinal grooves are formed on the outer
peripheral surface of the second cylindrical outside layer part;
and the first and second cylindrical outside layer parts have
different colors.
[0027] According to the second mode of the present invention, by
the above-described configuration, the cylindrical outside layer
part and the cylindrical inside layer part can be integrated, the
torsion of the whole of the grip can be prevented by the
combination of the longitudinal projecting strips and the
circumferential grooves, and the presence of the circumferential
grooves can resist the centrifugal force of the head at the
swinging time on the grip proximal end side. Therefore, the grip
feel on the grip proximal end side (the portion gripped by the left
hand for a right-handed person) is harder than the grip feel on the
grip distal end side (the portion gripped by the right hand), so
that the torsion of the portion gripped by the left hand, which
serves as the axis at the swinging time, becomes small. Therefore,
the ball hitting directivity is improved, and moreover, since the
cylindrical outside layer part is soft, an adverse influence of
ball hitting vibration is less liable to occur. Also, in the case
in which the cylindrical inside layer part is made of rubber, and
the grip is fixed to the shaft by using a common solvent for
mounting (white gas) and a double-faced adhesive tape, the solvent
vaporizes in a short period of time, and the fixing of the grip to
the shaft becomes firm in a short period of time of about a half
day or even less. Furthermore, since the first and second
cylindrical outside layer parts the colors of which are different
with the portion of the ring-shaped protrusion on the cylindrical
inside layer part being a boundary are coveringly formed, the
colors are divided clearly, so that the fashionability is improved,
and the division of roles of the right hand and the left hand is
perceived strongly.
[0028] A third mode of the present invention is a golf club grip
having a double construction in which a rubber cylindrical inside
layer part and a rubber cylindrical outside layer part are
provided, wherein a tungsten sheet having a thickness of 0.2 to 2.0
mm is interposed between the inside layer part and the outside
layer part in the back surface portion of the inside layer part.
The tungsten sheet may be interposed not only in the back surface
portion but also in the side portion and in the upper portion. As
the tungsten sheet, a sheet having a specific gravity of 8 or
larger, which is molded by mixing tungsten powder in a
thermoplastic resin material, may be used.
[0029] According to the third mode of the present invention, since
the golf club grip is configured as described above, the tungsten
sheet serves as a conventional counterbalancing member, so that
even a golf club, the weight of which is reduced, is easy to be
swung, and moreover, the appearance is good. The back surface
portion of grip in which the tungsten sheet is interposed swells
slightly and performs a function of preventing the slippage, and
can prevent the collision angle between the ball and the face from
being changed by the torsional deformation at the ball hitting
time. Also, in the case in which the conventional powder is used,
if the powder is mixed with rubber before vulcanization, there is a
possibility that the powder will scatter or leftover mixing occurs.
In the case in which the tungsten sheet is cut as in the present
invention, a prescribed weight can be added, and the variations in
weight as the grip decrease. Furthermore, since the thermoplastic
resin is used, rubber is vulcanized by adding heat of about 120 to
160.degree. C. Therefore, the resin material becomes fitted with
the mold at the molding time, and an effect of being deformed
(curved) properly with respect to rubber can be anticipated.
[0030] A fourth mode of the present invention is a golf club grip
having a double construction in which a cylindrical inside layer
part using a rubber compound having a large specific gravity and an
outside layer part using a rubber compound having a specific
gravity less than that of the inside layer part are provided,
wherein the length of the inside layer part is shorter than the
length of the outside layer part.
[0031] According to the fourth mode of the present invention, by
the above-described configuration, for example, the inside layer
part can be made a vulcanization molded product of rubber compound
in which metal powder or barium sulfate is kneaded, and the
specific gravity of this inside layer part can be made 1.3 to 1.6.
Therefore, the inside layer part serves as a conventional
counterbalancing member, so that even a golf club the weight of
which is reduced is easy to be swung. Moreover, the grip feel is
good, and the collision angle between the ball and the face can be
prevented from being changed by the torsional deformation at the
ball hitting time.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is an exploded perspective view showing a cylindrical
inside layer part and a cylindrical outside layer part of a golf
club grip in accordance with one embodiment of the present
invention.
[0033] FIG. 2 is a plan view of the cylindrical inside layer part
shown in FIG. 1.
[0034] FIG. 3 is a sectional view showing a state in which the golf
club grip shown in FIG. 1 is completed.
[0035] FIG. 4 is an exploded perspective view showing a cylindrical
inside layer part and a cylindrical outside layer part of a golf
club grip in accordance with another embodiment of the present
invention.
[0036] FIG. 5 is a plan view of the cylindrical inside layer part
shown in FIG. 4.
[0037] FIG. 6 is a sectional view showing a state in which the golf
club grip shown in FIG. 4 is completed.
[0038] FIG. 7 is a sectional view for explaining molding of a
cylindrical outside layer part of the golf club grip shown in FIG.
4.
[0039] FIG. 8 is an exploded perspective view showing a golf club
grip in accordance with still another embodiment of the present
invention.
[0040] FIG. 9 is a sectional view showing a state in which the golf
club grip shown in FIG. 8 is completed.
[0041] FIG. 10 is an exploded perspective view showing a golf club
grip in accordance with still another embodiment of the present
invention.
[0042] FIG. 11 is a sectional view for explaining vulcanization
molding of the golf club grip shown in FIG. 10.
[0043] FIG. 12 is a flow chart for explaining one example of a
method for manufacturing a tungsten sheet shown in FIG. 8 and FIG.
10.
[0044] FIG. 13 is a longitudinal sectional view of a golf club grip
in accordance with still another embodiment of the present
invention.
[0045] FIG. 14 is a transverse sectional view taken along the line
A-A of the golf club grip shown in FIG. 13.
[0046] FIG. 15 is a sectional view of a golf club grip in
accordance with still another embodiment of the present
invention.
[0047] FIG. 16 is a sectional view for explaining molding of the
golf club grip shown in FIG. 15.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0048] Embodiments of a golf club grip in accordance with the
present invention will now be described with reference to the
accompanying drawings.
[0049] First, an embodiment of the golf club grip shown in FIGS. 1
to 3 is explained. Both of a cylindrical inside layer part 1 and a
cylindrical outside layer part 2 of the golf club grip shown in
FIG. 1 are members made of rubber. The cylindrical inside layer
part 1 is molded first, this molded cylindrical inside layer part 1
is set in a mold as an insert member, and the cylindrical outside
layer part 2 is molded so as to cover the cylindrical inside layer
part 1. In FIG. 1, for convenience of explanation, these inner and
outside layer parts are shown as if being molded separately. After
the cylindrical outside layer part 2 has been molded, the
cylindrical inside layer part 1 is covered by the cylindrical
inside layer part 1.
[0050] The rubber used as the molding material for the cylindrical
inside layer part 1 and the cylindrical outside layer part 2
contains natural rubber (NR) as the main component. A rubber
compound in which, for example, 80 to 100 parts by weight of NR, 0
to 20 parts by weight of SBR (styrene-butadiene rubber) or EPDM, 1
part by weight of antiaging agent, 1 part by weight of stearic
acid, 10 to 30 parts by weight of carbon black, 5 to 10 parts by
weight of softening agent, 2 parts by weight of processing aid, 5
parts by weight of zinc oxide, 1 to 2 parts by weight of
vulcanization accelerator, 0.5 part by weight of vulcanization
accelerating additive, and 1 to 2 parts by weight of sulfur are
blended is vulcanization molded into a grip shape. In the
cylindrical inside layer part 1 and the cylindrical outside layer
part 2, the composition of the rubber compound is changed, and the
cylindrical inside layer part 1 is molded so as to be hard.
Therefore, in the cylindrical inside layer part 1, as the SBR, an
SBR containing 50% or more of styrene may be used. For the
cylindrical outside layer part 2, a cylindrical part that is formed
by molding and vulcanizing a rubber compound containing 45 to 90
parts by weight of diene-based rubber, 5 to 30 parts by weight of
ethylene-propylene binary copolymer and/or ethylene-propylene-diene
ternary copolymer, and 5 to 25 parts by weight of chlorobutyl
rubber can be used suitably. The diene-based rubber is preferably
at least one kind selected from the group consisting of natural
rubber, isoprene rubber, styrene-butadiene rubber,
nitrile-butadiene rubber, and chloroprene rubber. The use of such a
rubber compound provides a grip that has a high coefficient of
dynamic friction, is less liable to slip, has excellent wear
resistance and weather resistance, and therefore has high
durability and long service life. Furthermore, the grip formed of
the above-described rubber compound has excellent low-temperature
characteristics, is not sticky, and gives very good grip feel.
Also, a grip end 3 is colored by using silica, talc, or the like as
a reinforcing agent in place of carbon black and by adding a
pigment. Also, to increase the hardness, a resin containing 5 to 20
parts by weight of SBR containing 50% or more of styrene
(high-styrene SBR) may be added.
[0051] As shown in FIG. 2, the cylindrical inside layer part 1 is
formed with a plurality of longitudinal projecting strips 4, each
of which has a length of 8 to 11 cm from the grip end 3 side, a
thickness (projection height) of 0.2 to 0.6 mm, and a width of 0.6
to 1.5 mm, on the outer peripheral surface thereof. The interval
between the two longitudinal projecting strips 4 on the grip end 3
side may be 3 mm. The grip end 3 is formed of a rubber compound
harder than that of the cylindrical inside layer part 1, and is
integrated with the cylindrical inside layer part 1. Also, on the
distal end side (having a length of one-fourth to one-fifth the
entire length of the cylindrical inside layer part 1) of the
cylindrical inside layer part 1, projecting strips 5 are
formed.
[0052] The grip end 3 has a type A hardness as prescribed in JIS
K6253 (hereinafter, the term "hardness" means the type A hardness
as prescribed in JIS K6253) of 65 to 75, the cylindrical inside
layer part 1 has a hardness of 65 to 75, and the cylindrical
outside layer part 2 has a hardness of 40 to 50. The
above-described values of the hardness are nonrestrictive, and the
cylindrical outside layer part 2 may be softer than the cylindrical
inside layer part 1 in terms of physical property.
[0053] In the portion of the cylindrical outside layer part 2 that
covers the portion of the cylindrical inside layer part 1 in which
the longitudinal projecting strips 4 are formed, plural
circumferential grooves 6 are formed on the outer peripheral
surface thereof. The circumferential grooves 6 are so narrow that
the width of each of the grooves 6 is about 0.1 to 0.3 mm, and are
arranged in parallel at intervals of about 1.5 mm in the axis line
direction. Plural slantwise grooves 7 are also formed so as to
cross the circumferential grooves 6. These grooves 6 and 7 yield an
antislipping effect. The circumferential grooves 6 make it easy for
an opposing force to act in the grip portion against the
centrifugal force of the head at the time of swing. Also, on the
outer peripheral surface on the distal end side of the
circumferential grooves 6 of the cylindrical outside layer part 2,
plural longitudinal grooves 8 are formed, and also a plurality of
slantwise grooves 9 are formed so as to cross the longitudinal
grooves 8.
[0054] The entire length of the cylindrical inside layer part 1 is
made 1 to 4 cm longer than a half of the grip entire length (the
entire length including the grip end 3). If the difference between
the length of the cylindrical inside layer part 1 and a half of the
grip entire length exceeds 4 cm, the total weight of the grip
increases. Even if the cylindrical inside layer part 1 is
lengthened more than necessary, the improvement in function as a
grip is not observed.
[0055] Between the circumferential grooves 6 and the longitudinal
grooves 8 of the cylindrical outside layer part 2, a gap S.sub.2 is
provided. This gap S.sub.2 corresponds to a gap S.sub.1 located at
the distal end of the cylindrical inside layer part 1. At the upper
and lower ends of the gap S.sub.2, two annular grooves 6A are
formed.
[0056] As shown in FIG. 3, the grip end 3 is formed with an
engagement part 3A and a flange part 3B. The engagement part 3A is
engaged with and fixed to the rear end of the cylindrical inside
layer part 1. The outside diameter of the flange part 3B is equal
to the outside diameter on the proximal end side of the cylindrical
outside layer part 2. In the hollow portion surrounded by an inner
wall 1A of the cylindrical inside layer part 1 and in the hollow
portion surrounded by an inner wall 2A of the cylindrical outside
layer part 2, a shaft (not shown) is inserted, whereby the grip is
mounted on the shaft. The shaft and the grip are fixed to each
other as described below. For example, a double-faced adhesive tape
is stuck onto the shaft, a solvent for mounting is applied to this
tape and the inner wall surface of the shaft, and the shaft is
inserted into the hollow portion of the grip quickly. After about
ten hours has elapsed, the grip was cut out, and it was found that
both of the inner wall surface of shaft and the tape were in a dry
state.
[0057] The wall thicknesses of the cylindrical inside layer part 1
and the cylindrical outside layer part 2 are made such that the
wall thickness of the cylindrical inside layer part 1 is larger
than the wall thickness of the cylindrical outside layer part 2 at
least in the portion covering the cylindrical inside layer part 1.
The impact force at the time when a golfer hits a ball gives
torsional deformation to the grip, and this torsional deformation
depends greatly on the deformation of the soft cylindrical outside
layer part 2. However, since the cylindrical inside layer part 1
that is hard and thick in wall thickness is covered by the
cylindrical outside layer part 2 that is soft and thin in wall
thickness, the torsional rigidity of the whole of grip is improved.
Also, the longitudinal projecting strips 4 formed on the
cylindrical inside layer part 1 contribute to the improvement in
the torsional rigidity of grip. If the torsional rigidity is
improved, the ball hitting directivity is also improved.
[0058] Next, an embodiment of the golf club grip shown in FIGS. 4
to 7 is explained. In this embodiment, the same reference numerals
are applied to the elements that are the same as those in the
embodiment of the golf club grip shown in FIGS. 1 to 3, and the
detailed explanation thereof is omitted. In this embodiment, as
shown in FIGS. 4 and 5, between the proximal end of the projecting
strips 5 and the distal end of the longitudinal projecting strips 4
of the cylindrical inside layer part 1, a ring-shaped protrusion 10
is formed along the circumferential direction. On both sides of
this protrusion 10, a pair of rings 10A and 10B each having a wall
thickness larger than the thicknesses (protrusion heights) of the
longitudinal projecting strips 4 and the protrusion 10 are formed.
The ring-shaped protrusion 10 is formed so as to be thicker than
the rings 10A and 10B.
[0059] In a portion of a first cylindrical outside layer part 2A
that covers the portion of the cylindrical inside layer part 1 in
which the longitudinal projecting strips 4 are formed, that is, the
portion between the grip end 3 and the ring-shaped protrusion 10,
the plurality of circumferential grooves 6 are formed on the outer
peripheral surface thereof. Also, on the outer peripheral surface
of a second cylindrical outside layer part 2B formed on the distal
end side of the ring-shaped protrusion 10 of the cylindrical inside
layer part 1, the plurality of longitudinal grooves 8 are formed,
and the plurality of slantwise grooves 9 are also formed so as to
cross the longitudinal grooves 8. The first and second cylindrical
outside layer parts 2A and 2B divided by the ring-shaped protrusion
10 use rubbers having colors different from each other.
[0060] The first cylindrical outside layer part 2A and the second
cylindrical outside layer part 2B the colors of which are divided
clearly in the portion of the ring-shaped protrusion 10 can be
molded by changing the hardness of rubber. The second cylindrical
outside layer part 2B (the distal end side) is preferably harder
than the first cylindrical outside layer part 2A (the proximal end
side). It is preferable that the second cylindrical outside layer
part 2B have a hardness of 45 to 55 because of its thin wall, and
the first cylindrical outside layer part 2A be so soft that the
longitudinal projecting strips 4 of the cylindrical inside layer
part 1 can be felt (for example, the hardness being 35 to 45). This
configuration can be realized, for example, by increasing the
blending ratio of carbon black or silica of the inside layer part 1
as compared with the outside layer part 2.
[0061] The grip end 3 has a color different from that of a body
portion (the portion excluding the grip end 3) of the cylindrical
inside layer part 1. Since materials having different colors are
vulcanization molded, as shown in FIGS. 4 and 5, the boundary
thereof becomes wavy, and the colors are less liable to be divided
clearly.
[0062] The first cylindrical outside layer part 2A and the second
cylindrical outside layer part 2B the colors of which are different
are molded as described below. First, the cylindrical inside layer
part 1 is molded by injection molding. At this time, to mold a
hollow portion in the cylindrical inside layer part 1, as shown in
FIG. 7, the material is injected to around a mandrel 11, the
mandrel 11 is not removed after molding, and the cylindrical inside
layer part 1 with the mandrel 11 is inserted into a space
surrounded by an upper mold 12, a lower mold 13, and a back end
mold 11A. At this time, a hole 3C located on the central axis of
the grip end 3 is fitted on a pin of the back end mold 11A to
prevent the mandrel 11 from being off-center. Also, on the grip
proximal end side and the grip distal end side of the ring-shaped
protrusion 10, rubber sheets 14 and 15 having different colors are
wound on the cylindrical inside layer part 1. The upper and lower
molds 12 and 13 are fastened to each other to compression mold the
rubber sheets 14 and 15, and the resulting rubber sheet 14 becomes
the first cylindrical outside layer part 2A, and the rubber sheet
15 becomes the second cylindrical outside layer part 2B.
[0063] Furthermore, an embodiment of the golf club grip shown in
FIGS. 8 to 12 is explained. In this embodiment, the same reference
numerals are applied to the elements that are the same as those in
the embodiments of the golf club grip shown in FIGS. 1 to 3 and
FIGS. 4 to 7, and the detailed explanation thereof is omitted. In
this embodiment, as shown in FIGS. 8 and 9, a tungsten sheet 20 is
used in addition to the cylindrical inner and outside layer parts 1
and 2. As shown in FIG. 10, the inside layer part 1 can also be
provided with the ring-shaped protrusion 10 and the pair of rings
10A and 10B.
[0064] As shown in FIG. 11, the inside layer part 1 with the
mandrel 11 is inserted into a space surrounded by the upper mold
12, the lower mold 13, and the back end mold 11A, and the tungsten
sheet 20 is placed in a portion located in the back surface portion
of the inside layer part 1. The inside layer part 1 with the
mandrel 11 and the tungsten sheet 20 are set in the mold as an
insert member, and the outside layer part 2 is molded so as to
cover the inside layer part 1. In the case in which the outside
layer part 2 having the first outside layer part 2A and the second
outside layer part 2B is molded, as shown in FIG. 11, on the grip
proximal end side and the grip distal end side of the ring-shaped
protrusion 10, the rubber sheets 14 and 15 having different colors
are wound on the inside layer part 1. The method for molding the
grip is not limited to the above-described method. For example,
vulcanization (molding) may be accomplished using a mold for
compression by holding the tungsten sheet 20 between unvulcanized
(not-molded) rubber sheets for the inside layer part and the
outside layer part. In this case as well, an integrated grip in
which the tungsten sheet 20 is placed between the outside layer
part 2 and the inside layer part 1 can be obtained.
[0065] The tungsten sheet 20 is (injection) molded by mixing
tungsten powder in a pellet-form thermoplastic resin material. The
thickness thereof is 0.2 to 2.0 mm, and the specific gravity
thereof is in the range of 8 to 13. For example, the tungsten sheet
20 having a thickness of 2 mm, a width of 5 mm, and a length of 100
mm had a specific gravity of 12 and a weight of 12 g. Also, as the
tungsten sheet 20 having the same specific gravity and the same
weight, a tungsten sheet having a thickness of 1 mm, a width of 10
mm, and a length of 100 mm was able to be obtained. For such a
tungsten sheet 20, a tungsten sheet having a specific gravity of 11
or more is preferably used as a counterbalancing member. Also, such
a tungsten sheet 20 provides specific gravity performance equal to
or greater than that of lead, and requires no control of usage and
disposal, unlike lead. Furthermore, such a tungsten sheet 20 has
great flexibility. Therefore, it can be bent freely, and can fit a
curved or intricately shaped portion, that is, a portion formed
with the longitudinal projecting strips 4 of the inside layer part
1 (an irregularly-shaped portion) in this embodiment. Furthermore,
this tungsten sheet 20 can be worked by scissors or the like and
can easily be caused to fit an intricately shaped portion by being
heated because it is thermoplastic. As a thermoplastic resin used,
a vinyl resin, phenolic resin, polyethylene resin, olefin
elastomer, and styrene elastomer are suitable. Also, if the
tungsten sheet 20 is formed with holes 20A or slits 20B, it is
fixed more stably to between the inside layer part 1 and the
outside layer part 2. The tungsten sheet 20 not having these holes
20A or slits 20B or the tungsten sheet 20 having either one of them
can also be used.
[0066] FIG. 12 is a flow chart for explaining one example of a
method for manufacturing the tungsten sheet 20. As shown in FIG.
12, first, 90 wt % or more of tungsten metal powder is kneaded with
thermoplastic elastomer by using an agitation mixer such as a
kneader. By doing this, a composite material of tungsten and
elastomer is obtained. The specific gravity of this composite
material is preferably in the range of 8 to 13. The composite
material is extrusion molded or injection molded into a sheet,
whereby the tungsten sheet is obtained. The tungsten metal powder
may be mixed with and regulated by any additive agent (plasticizer,
release agent, lubricant, etc.) before being kneaded with
elastomer.
[0067] Finally, an embodiment of the golf club grip shown in FIGS.
13 to 16 is explained. In this embodiment, the same reference
numerals are applied to the elements that are the same as those in
the embodiments of the golf club grip shown in FIGS. 1 to 3 and
FIGS. 4 to 7, and the detailed explanation thereof is omitted. In
this embodiment, a cylindrical inside layer part 30 is
vulcanization molded by kneading barium sulfate and/or metal powder
in the rubber compound, for example, in the case in which the
inside layer part is molded first, that is, the inside layer part
30 is a rubber compound having a large specific gravity. Next, the
outside layer part 2 is molded so as to cover the inside layer part
30. FIG. 14, which is a sectional view taken along the line A-A of
FIG. 3, shows a shaft 31 in addition to the grip. Also, as shown in
FIG. 15, the inside layer part 30 can be provided with the
ring-shaped protrusion 10 and the pair of rings 10A and 10B. The
reason why the inside layer part 30 is formed by the rubber
compound having a high specific gravity and the outside layer part
2 is formed by the rubber compound having a low specific gravity is
that the rubber compound constituting the inside layer part 30
contains barium sulfate and metal powder, and thus, there are
possibilities that the rubber compound of the inside layer part 30
will become brittle and the touch will be deteriorated. Both of the
inside layer part 30 and the outside layer part 2 can be molded by
molding an unvulcanized sheet and by compression molding these
sheets simultaneously.
[0068] The rubber used as the molding material for the inside layer
part 30 contains natural rubber (NR) as the main component. Barium
sulfate having a blending ratio of 15 parts by weight can be
kneaded in a rubber compound in which, for example, 80 to 100 parts
by weight of NR, 0 to 20 parts by weight of EPDM, 1 part by weight
of antiaging agent, 1 part by weight of stearic acid, 10 to 30
parts by weight of carbon black, 5 to 10 parts by weight of
softening agent, 2 parts by weight of processing aid, 5 parts by
weight of zinc oxide, 1 to 2 parts by weight of vulcanization
accelerator, 0.5 part by weight of vulcanization accelerating
assistant, and 1 to 2 parts by weight of sulfur are blended.
Together with or in place of barium sulfate, metal powder may be
kneaded. As the metal powder, a powder of tungsten, copper, lead,
or the like can be used.
[0069] As shown in FIG. 16, the inside layer part 30 is molded by
injecting the material to around the mandrel 11. Then, the inside
layer part 30 with the mandrel 11 is set in a space in the mold,
and the outside layer part 2 is molded so as to cover the inside
layer part 30.
EXAMPLES
[0070] The inside layer part 30 was formed by the rubber compound
described below. In this rubber compound, barium sulfate and/or
metal powder were mixed. A blend example in which barium sulfate
and/or metal powder were not mixed is shown in Table 1 as a basic
blend example. Examples 1 to 7 are shown in Table 2 to Table 8. The
weight of grip of example 1 was about 50 g. The unit in the tables
is parts by weight. In the evaluation of "rubber kneading
workability" in the tables, "excellent" is indicated by "A", "good"
by "B", and "somewhat difficult" by "C".
TABLE-US-00001 TABLE 1 Basic blend example Blended material of
rubber compound Blending ratio Natural rubber (NR) 85
Ethylene-propylene-diene rubber (EPDM) 15 Antiaging agent 1 Stearic
acid 1 Carbon black 15 Silica (SiO.sub.2) 5 Barium sulfate 0
Softening agent 10 Processing aid 2 Zinc oxide 5 Vulcanization
accelerator 1.5 Vulcanization accelerating assistant 0.5 Sulfur 1.8
Specific gravity 1.1 Rubber kneading workability A Increase in grip
weight 0
TABLE-US-00002 TABLE 2 Example 1 Blended material of rubber
compound Blending ratio Natural rubber (NR) 85
Ethylene-propylene-diene rubber (EPDM) 15 Antiaging agent 1 Stearic
acid 1 Carbon black 15 Silica (SiO.sub.2) 0 Barium sulfate 25
Softening agent 10 Processing aid 2 Zinc oxide 5 Vulcanization
accelerator 1.5 Vulcanization accelerating assistant 0.5 Sulfur 1.8
Specific gravity 1.6 Rubber kneading workability C Increase in grip
weight About 10 g increase
TABLE-US-00003 TABLE 3 Example 2 Blended material of rubber
compound Blending ratio Natural rubber (NR) 85
Ethylene-propylene-diene rubber (EPDM) 15 Antiaging agent 1 Stearic
acid 1 Carbon black 15 Silica (SiO.sub.2) 0 Barium sulfate 20
Softening agent 10 Processing aid 2 Zinc oxide 5 Vulcanization
accelerator 1.5 Vulcanization accelerating assistant 0.5 Sulfur 1.8
Specific gravity 1.5 Rubber kneading workability B Increase in grip
weight About 8 g increase
TABLE-US-00004 TABLE 4 Example 3 Blended material of rubber
compound Blending ratio Natural rubber (NR) 85
Ethylene-propylene-diene rubber (EPDM) 15 Antiaging agent 1 Stearic
acid 1 Carbon black 15 Silica (SiO.sub.2) 5 Barium sulfate 15
Softening agent 10 Processing aid 2 Zinc oxide 5 Vulcanization
accelerator 1.5 Vulcanization accelerating assistant 0.5 Sulfur 1.8
Specific gravity 1.4 Rubber kneading workability B Increase in grip
weight About 7 g increase
TABLE-US-00005 TABLE 5 Example 4 Blended material of rubber
compound Blending ratio Natural rubber (NR) 85
Ethylene-propylene-diene rubber (EPDM) 15 Antiaging agent 1 Stearic
acid 1 Carbon black 15 Silica (SiO.sub.2) 5 Barium sulfate 10
Softening agent 10 Processing aid 2 Zinc oxide 5 Vulcanization
accelerator 1.5 Vulcanization accelerating assistant 0.5 Sulfur 1.8
Specific gravity 1.3 Rubber kneading workability A Increase in grip
weight About 5 g increase
TABLE-US-00006 TABLE 6 Example 5 Blended material of rubber
compound Blending ratio Natural rubber (NR) 85
Ethylene-propylene-diene rubber (EPDM) 15 Antiaging agent 1 Stearic
acid 1 Carbon black 15 Silica (SiO.sub.2) 5 Barium sulfate 5
Softening agent 10 Processing aid 2 Zinc oxide 5 Vulcanization
accelerator 1.5 Vulcanization accelerating assistant 0.5 Sulfur 1.8
Specific gravity 1.2 Rubber kneading workability A Increase in grip
weight About 2 g increase
TABLE-US-00007 TABLE 7 Example 6 Blended material of rubber
compound Blending ratio Natural rubber (NR) 85
Ethylene-propylene-diene rubber (EPDM) 15 Antiaging agent 1 Stearic
acid 1 Carbon black 15 Silica (SiO.sub.2) 5 Barium sulfate 5
Tungsten metal powder 2 Softening agent 10 Processing aid 2 Zinc
oxide 5 Vulcanization accelerator 1.5 Vulcanization accelerating
assistant 0.5 Sulfur 1.8 Specific gravity 1.5 Rubber kneading
workability A Increase in grip weight About 8 g increase
TABLE-US-00008 TABLE 8 Example 7 Blended material of rubber
compound Blending ratio Natural rubber (NR) 85
Ethylene-propylene-diene rubber (EPDM) 15 Antiaging agent 1 Stearic
acid 1 Carbon black 15 Silica (SiO.sub.2) 5 Barium sulfate 5
Tungsten metal powder 1 Softening agent 10 Processing aid 2 Zinc
oxide 5 Vulcanization accelerator 1.5 Vulcanization accelerating
assistant 0.5 Sulfur 1.8 Specific gravity 1.4 Rubber kneading
workability A Increase in grip weight About 5 g increase
[0071] Barium sulfate is used for improving the performance of
rubber, for example, the physical properties of vulcanized rubber
and the workability of unvulcanized rubber and for increasing the
quantity for cost reduction, and is contained in a white filler. As
a black filler, carbon black was used. The barium sulfate used is
settling barium sulfate in which the particles are amorphous, very
fine, and soft, and the specific gravity is 4.3. The specific
gravity of carbon black serving as a filler is 1.8, the specific
gravity of silica (SiO.sub.2) is 2.1, the specific gravity of
calcium carbonate is 2.6, and the specific gravity of tungsten
powder is 19.3. In the examples given in Table 7 and Table 8, the
grip weight may be increased by mixing only barium sulfate of
filler, which is compatible with rubber. However, a small amount of
tungsten powder was mixed to attain the intended weight. The
tungsten metal powder used was subjected to coupling treatment to
prevent oxidation.
[0072] While the invention has been described in connection with a
preferred embodiment, it is not intended to limit the scope of the
invention to the particular form set forth, but on the contrary, it
is intended to cover such alternatives, modifications, and
equivalents as may be included within the spirit and scope of the
invention as defined by the appended claims.
* * * * *